Brazing and soldering are two methods commonly used to join two similar or dissimilar metals together. These processes typically involve joining metal components together by disposing a brazing composition such as an aluminum or metal alloy adjacent to or between the faying surfaces, i.e., the surfaces to be joined. The brazing filler alloy and the faying surfaces are then heated to the brazing temperature, typically above the melting temperature of the braze alloy but below the melting temperature of the components to be joined. The brazing composition then melts, flows into the joint by capillary action and forms a fillet and seal that bonds the faying surfaces.
In most cases, these processes require a chemical flux in addition to the filler alloy. The flux prepares the base metals to accept the filler alloy which results in a strong bond. Fluxes are generally grouped under two categories: corrosive (must be removed) and non-corrosive (residues are left on the part).
Historically, the alloy and flux are applied as two separate steps. In recent years however, an increasing number of options have been developed that combine the filler alloys and fluxes in one complete form. These developments have taken place with brazing alloys that are aluminum based and silver based.
For instance, Omni Technologies Corporation (Epping, N.H.) developed a flux core wire, which is sold under the trademark SIL-CORE™. In order to accomplish this, Omni takes aluminum in the form of narrow sheet, deposits a quantity of powdered flux down the middle, and then form rolls the narrow sheet around the flux. This material is then put through draw dies to reduce the diameter and compact the flux inside. From this process, Omni offers several wire diameters as well as different flux compositions. In addition, the amount of flux can be changed as needed. This material is available on spools, large coils and custom fabricated shapes. The inventors of the present invention believe Omni uses a flux sold by Solvay Chemical Company under the name NOCOLOK®. NOCOLOK® brand is one of the most widely recognized non-corrosive aluminum fluxes. This product is described in U.S. Pat. No. 5,781,846, which is hereby incorporated by reference as if fully set forth herein. Omni claims the SIL-CORE™ product does not contain a binding agent.
The S.A. Day Corporation (Buffalo, N.Y.) produces an aluminum flux coated rod sold under name DAYROD. This rod includes an aluminum wire cut to 12 inch rods, and dipped in an aluminum flux bath. After dipping, the rods are hung to dry. Day does not use NOCOLOK® brand flux. Instead, Day uses a similar formulation which is mixed with a polymer-based binder system. This binder allows for the flux to remain ductile and not brittle. The flux coated rods can be bent or twisted and the flux will not fall off.
Day also produces a flux coated ring. Day purchases metallic rings from Bellman-Melcor, Inc. The rings are then loaded on a machine that “paints” a thin coating of flux on the outside edge of each ring. While the end product is acceptable, it is very slow to produce and consequently very expensive. Similar to the rods, the rings can be handled roughly and the flux remains intact.
Protechno-Richard (France) offers a product very similar to the Omni product.
Kin-Met (Korea) produces an extruded product. A powdered form of aluminum braze alloy is mixed with powdered flux. The combination is pressurized and extruded into final form.
Wolverine and Omni teamed up to create a flux coating for silver based materials. Made from a ductile binder system, this technology is sold under the name SILVACOTE™. SILVACOTE™ is a continuously coated, flux-coated brazing material.
U.S. Pat. No. 7,858,204, which is hereby incorporated by reference as if fully set forth herein, describes a wire for use in a brazing or soldering operation. The wire includes an elongated body of a metallic material, a channel having an opening formed along a length of the elongated body, the opening having a width of about 30% to 70% of a major axis of a cross-section of the elongated body, a cured flux solution formed by curing a flux solution comprising a polymer-based binder material and a flux material within the channel and along at least a portion of the length of the elongated body with a surface of the cured flux solution being exposed through the opening in the channel. The wire is formed into an annular ring, and the cured flux solution within the channel forms a portion of an inner wall of the annular ring. The '204 patent also describes alternative embodiments, one of which includes a plurality of flux solution-containing channels formed in a wire. The channels are formed along a transverse length of the wire. The wire maybe formed into an annular ring such that the channels bearing the flux solution form a portion of an inner wall of the ring. The outer wall of the ring includes a section or portion of each channel and thus the flux solution within each channel also forms a portion of the outer wall of the ring.
U.S. Pat. No. 8,274,014 was issued from a continuation-in-part application claiming priority from the application from which the '204 patent issued. The '014 patent is also incorporated by reference as if fully set forth herein. The '014 patent is directed to wire for brazing or soldering comprising a first channel and a second channel, both extending lengthwise along the central axis of the wire. The first and second channels comprise a pair of sidewalls extending lengthwise along the central axis separated by a transverse base. Each sidewall extends radially outwardly from the base and forming an angle with the base greater than 90 degrees;
Despite the advancement provided by the '204 and '014 patents, there is a need for a brazing or soldering wire that can be used to create a better joint between connected parts. It would be an advancement in the art of brazing or soldering wire to provide such a wire capable of forming a larger joint area with improved distribution of flux over the area of the part or parts to be joined.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior brazing or soldering wires of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.